1. Technical Field
The present disclosure relates to a cloth-holder frame transfer apparatus for a sewing machine, which assists transfer of a cloth-holder frame by an external force when the external force has been applied to the cloth-holder frame by an operator.
2. Description of the Related Art
Embroidery sewing machines have conventionally been provided with a needlebar lifting mechanism which lifts up and down a needlebar having a lower end to which a sewing needle is attached, a thread seizing mechanism having a rotary hook, a cloth-holder frame which holds workpiece cloth so that stitches are formed on the workpiece cloth and a cloth-holder frame transfer apparatus which transfers the cloth-holder frame while holding the cloth-holder frame in a horizontal state. An embroidery pattern is sewn onto the workpiece cloth held by the cloth-holder frame in cooperation among the needlebar lifting mechanism, the thread seizing mechanism, the cloth-holder frame transfer apparatus and the like. See JP-A-2004-254987, for example.
The cloth-holder frame transfer apparatus comprises a carriage to which a cloth-holder frame is detachably attachable and a carriage driving mechanism having a feed motor which moves the carriage in two directions perpendicular to each other on a horizontal plane. A stepping motor or DC servomotor is applied to the feed motor. Furthermore, some of the conventional cloth-holder frame transfer apparatuses are provided with a rotary encoder detecting an amount of displacement of the feed motor so that results of detection are utilized for control of the feed motor.
When the operator designates a desired embroidery pattern and turns on a start switch with a cloth-holder frame being attached to the carriage, a control device of the embroidery sewing machine controls the needlebar lifting mechanism and the thread seizing mechanism (sewing machine motor). Furthermore, the control device controls the carriage driving mechanism (feed motor) so that the cloth-holder frame is automatically transferred by the cloth-holder frame transfer apparatus, whereby the designated embroidery pattern is automatically sewn on the workpiece cloth.
In the above-described case, a control device of the cloth-holder frame transfer apparatus reads embroidery data defining a plurality of needle locations regarding the designated embroidery pattern and controls the carriage driving mechanism so that the workpiece cloth is moved to a location where the needle is capable of dropping to a subsequent needle location when the sewing needle is assuming a needle-up position where the sewing needle is located higher than the workpiece cloth.
On the other hand, JP-A-2006-43232 discloses a sewing machine which is switchable between an embroidery sewing mode and a normal sewing mode. The sewing machine disclosed in the publication has been put to practice. In the embroidery sewing mode, an embroidery machine including a carriage and a carriage driving mechanism is detachably attached to a sewing machine bed. The cloth-holder frame is supported horizontally and automatically transferred as described above, whereby an embroidery pattern is sewn on the workpiece cloth. In the normal sewing mode, the embroidery machine is detached from the bed, and the workpiece cloth is transferred along a needle plate so that a normal pattern such as a satin pattern or the like is sewn on the workpiece cloth.
In the above-described type sewing machine, the workpiece cloth is fed in a predetermined direction by a feed dog while being pressed against a needle plate by a presser foot, in the same manner as in general sewing machines. In this case, the operator changes the direction of the workpiece cloth with his or her hand being put on the workpiece cloth, whereby the direction of stitches of an ordinary pattern can be changed relative to the workpiece cloth. An amount of feed of the workpiece cloth by the feed dog (stitch pitch) can be set before or during sewing. A sewing speed is adjustable by operation of a sewing speed knob, a foot controller or the like.
The sewing machine dedicated to embroidering as disclosed by the above-mentioned JP-A-2004-254987 is arranged so as to carry out sewing based on embroidery data of embroidery pattern. Accordingly, this sewing machine cannot carry out a sewing manner in which the workpiece cloth is sewn while the operator transfers the workpiece cloth along the needle plate thereby to change the stitch direction freely at a suitable stitch pitch.
When the embroidery machine is detached in the sewing machine of the above-mentioned JP-A-2006-43232 and the sewing machine is switched to the normal sewing mode, a normal pattern can be sewn while the stitch direction is changed at a suitable stitch pitch. However, the embroidery machine needs to be attached to and detached from the sewing machine in order that the sewing machine may be switched between the normal sewing mode and the embroidery sewing mode. As a result, a detaching or attaching work is troublesome, resulting in inconvenience. In view of these circumstances, it has been considered that sewing would be carried out by a sewing machine capable of sowing an embroidery pattern, such as disclosed in the above-mentioned documents, so that the carriage driving mechanism would be rendered non-operative and the operator would manually apply an external force to the cloth-holder frame attached to the carriage to move the cloth-holder frame freely.
However, the carriage and the feed motor of the carriage driving mechanism are connected to each other so as to be operated together. Accordingly, the carriage needs to be moved against detent torque acting on the feed motor or load applied to the carriage driving mechanism even when electric supply to the feed motor is interrupted such that the carriage driving mechanism is non-operative. As a result, moving the cloth-holder frame attached to the carriage necessitates a large external force, and it is difficult to move the cloth-holder frame smoothly in a desired direction. More specifically, it is difficult to sew the workpiece cloth held by the cloth-holder frame at a suitable stitch pitch with the stitch direction being changed freely and this has little practicability.
In general sewing machines, workpiece cloth is fed by a feed dog while being pressed against a needle plate by a presser foot. Accordingly, there is a problem that it is difficult for beginners to change the stitch direction desirably by smoothly changing the direction of the workpiece cloth during sewing of an ordinary pattern. Furthermore, an amount of feed of the workpiece cloth by the teed dog (stitch pitch) needs to be set before or during sewing, and a sewing speed needs to be adjusted by the operation of a sewing speed knob, fool controller or the like. This results in an increase in an amount of operation and accordingly inconvenience.